This invention relates to an electro-adhesion device.
Electro-adhesion is the process of creating a charge in an object and thereby attracting it to a special surface. Electro-adhesion devices, for attracting a non-magnetic object such as paper, have not been introduced as consumer products due to the fact that they are either ineffective, in that they do not create a sufficient adhesion force, or very expensive to make due to the complexity of these devices.
A further problem is that it is very difficult to create one adhesion device that attracts objects of a variety of materials with suitable force. It is this application of the invention which should predominantly but not exclusively be borne in mind.
According to the invention there is provided an electro-adhesion device which includes
a base; and
at least two thin electrically conductive electrodes located apart from each other on the base so as to define an electro-adhesion surface so that, in use, when the electrodes are energised and an object to be attracted is placed adjacent the electro-adhesion surface, the object is attracted to the electro-adhesion surface by a suitably high adhesion force.
The electrodes may be located on one side of the base so that adjacent electrodes form an electrode pair, which electrode pair is energised, in use, so as to be oppositely polarised thereby causing a charge differential in a part of the object adjacent that electrode pair which in turn causes the object to be attracted to the electro-adhesion surface.
The electrodes may be located on opposite sides of the base when the base is made of a substance having a high dielectric constant (Epsilon), typically of at least 5. Electrodes of an electrode pair may be located on opposite sides of the base, which electrode pair is energised, in use, so as to be oppositely polarised thereby causing a charge differential in a part of the object adjacent that electrode pair which in turn causes the object to be attracted to the electro-adhesion surface. Electrodes on the same side of the base may be oppositely polarised to electrodes on the opposite side of the base thereby increasing a maximum withstand voltage between electrodes.
Each of the electrodes may have an outer surface facing away from the base which outer surface defines at least a part of the electro-adhesion surface and which outer surface has dimensions in any direction greater than the distance from such outer surface to the base, which distance is the thickness of the electrode. The electrode is typically extremely thin so as to limit charge build-up between adjacent electrodes. The electrodes are typically less than 5 xcexcm thick.
The electrodes may be silkscreen electrodes. The electrodes may be vapour deposition electrodes.
The electro-adhesion device may be configured so that as little air as possible is trapped between adjacent electrodes.
The electrodes may be elongate electrodes located substantially parallel to each other on a side of the base.
Adjacent electrodes may be located apart from each other by a minimum distance which is related to a maximum withstand voltage between the electrodes before flashover occurs. As the electro-adhesion force is proportional to the voltage between an electrode pair, the minimum distance may be selected so that an appropriate voltage is accomplished between an electrode pair in order to accomplish a sufficient electro-adhesion force without flashover occurring. Adjacent electrodes may be located apart from each other by a fixed or varying distance greater than or equal to the minimum distance.
The electrodes may be shaped to limit sharpness of corners of the electrodes thereby reducing the possibility of flashover occurring.
The shapes of the outer surfaces of the electrodes may be selected depending on the material composition of the object to be attracted.
The electrodes of at least one electrode pair may have outer surfaces having large surface areas in order to attract metals. Typically, the electro-adhesion device for metals only includes two oppositely polarised electrodes separated by a single separation gap between them.
The electrodes of at least one electrode pair may have outer surfaces having small surface areas in order to attract non-metals.
The outer surfaces of the electrodes may be shaped so that they have varying surface areas so that, in use, the object to be attracted may be made from any one of a variety of materials including metals and non-metals, the object thereby being attracted with suitable electro-adhesion force regardless of the material. The varying surface area of the electrodes may be repetitive lengthwise along the electrodes. The outer surface of at least two of the electrodes may have a linear border on one side and a sinusoidal border on an opposite side so that the width of each electrode varies sinusoidally lengthwise along the electrode. Accordingly, the electrodes may be configured so that the sinusoidal border of one electrode is aligned adjacent the sinusoidal border of an adjacent electrode and so that the linear border of one electrode is aligned adjacent the linear border of an adjacent electrode, such that the minimum distance between adjacent electrodes remains fairly constant.
Typically, the electrodes of an electrode pair are oppositely polarised by a low current with a relatively high voltage. The electrodes may be polarised by way of a DC voltage. The low current is typically less than 5 xcexcA DC and the relatively high voltage more than 1500 V DC.
The base is typically made of a substance chosen to minimise leakage from the electro-adhesion device such as a substance having a high bulk resistivity of at least 1016 xcexa9/m.
The electro-adhesion device may comprise at least one layer formed by electrodes and a layer formed by the base. Accordingly the base may be thin so as to define a layer of the electro-adhesion device.
The profile of the base on which the electrodes are located typically determines the profile of the electro-adhesion surface. Accordingly, the profile of the base on which the electrodes are located may be shaped so as to correspond to the shape of a portion of the object to be attracted, which portion is the portion which is placed adjacent the electro-adhesion surface. This serves to minimise, in use, air gaps between the electro-adhesion surface and the object to be attracted.
In a preferred embodiment of the invention, the profile of the base on which the electrodes are located is typically flat, but in others it may follow any profile.
The base on which the electrodes are located is typically smooth. Such smoothness may be defined as having a surface variation of less than 0.01 xcexcm.
The electro-adhesion device may include an insulating cover over the electrodes so that an outer side of the insulating cover defines the electro-adhesion surface. The cover is typically as thin as possible as the electro-adhesion force is inversely proportional to the distance between the electrodes and the object to be attracted. The cover may be thinner than 100 xcexcm.
The cover may be in the form of a thin film. The film may be applied as a laminate.
The cover may be in the form of a coating. The coating may be applied as a spray on, dip in, or any other suitable means of application.
The cover is typically made from a substance having a high surface relative resistivity. The resistivity is typically more than 1016 xcexa9.
The cover may be made of a substance having a high dielectric constant (Epsilon), typically of at least 6.
The cover may be smooth. Such smoothness may be defined as having a surface variation of less than 0.01 xcexcm.
The base may be in the form of an insulating cover as described above. Accordingly the electrodes may be sandwiched between two covers so that the electro-adhesion device includes two electro-adhesion surfaces.
The invention is not limited to the specific embodiments contained in this specification and all variations falling within the spirit of the invention are included in the scope of the invention as if specifically listed.